Persona:
Varela Díez, Fernando

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0000-0002-3564-1639
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Varela Díez
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Fernando
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20232
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Autor: Varela Díez, Fernando × Fecha de inicio: 2020 ×

Resultados de la búsqueda

Mostrando 1 - 2 de 2
  • Miniatura
    Publicación
    A New Thermodynamic Model to Approximate Properties of Subcritical Liquids
    (MDPI, 2023-06-29) Sánchez Orgaz, Susana; González Fernández, M. Celina; Varela Díez, Fernando; Rodríguez Laguna, Javier
    In order to obtain the thermodynamic properties of compressed liquids, it is usual to consider them as incompressible systems, since liquids and solids are well represented by this thermodynamic model. Within this model, there are two usual hypotheses that can be derived in two different submodels: the strictly incompressible (SI) model, which supposes a constant specific volume 𝑣=𝑣0, and a more general model, called temperature-dependent incompressible (TDI) model, which relates a specific volume to temperature, 𝑣=𝑣(𝑇). But, usually, this difference ends here in the thermal equation of state, and only the SI model was developed for caloric and entropic equations. The aim of this work is to provide a complete formulation for the TDI model and show where it can be advantageously used rather than the SI model. The study concludes that the proposed model outperforms the traditional model in the study of subcritical liquid. One conceivable utilization of this model is its integration into certain thermodynamic calculation software packages (e.g., EES), which integrate the more elementary SI model into its code for certain incompressible substances.
  • Miniatura
    Publicación
    Using Fourier series to obtain cross periodic wall response factors
    (Taylor & Francis, 2023-11-22) Theirs, Eduardo; Sánchez Orgaz, Susana; Varela Díez, Fernando; González Gaya, Cristina
    Wall periodic response factors are a very usual calculation method of transient heat transfer through building envelope elements (walls, roofs …) in steady periodic conditions, used in popular heat load calculation procedures as ASHRAE’s RTS method [Spitler, Jeffrey D., Daniel E. Fisher, and Curtis O. Pedersen. 1997. “The Radiant Time Series Cooling Load Calculation Procedure.” ASHRAE Transactions 103 (2): 503–515]. This response factors, time sampled heat flux responses of a multi-layer wall to a 24h-periodic unit triangle function, can be obtained by means of multiple methods: Laplace’s method, state space method, frequency domain methods, etc. These methods are numerical since there is no analytical way of obtaining these response factors. The aim of this work is, taking advantage of the periodic nature of excitations, use Fourier series to represent boundary conditions, and this way find an easier and less computationally demanding procedure to calculate these response factors. Additionally, the convergence of these Fourier series will be analysed to determine the minimum set of frequencies needed to ensure a fixed admissible error for wall periodic response factors.